Various prior art processes involve the conversion of paraffinic hydrocarbons to aromatics. For example U.S. Pat. No. 4,347,395 to Chu et al discloses a process for producing aromatic compounds by contact of a gaseous hydrocarbon feedstock containing predominantly paraffinic hydrocarbons of two to six carbon atoms with oxygen or air in the presence of a catalyst system to convert at least a portion of the feed hydrocarbons to liquid aromatic hydrocarbons. The catalyst system comprises a crystalline zeolite catalyst in combination with a metal or metal oxide oxidative dehydrogenation component. Suitable dehydrogenation components include ferric oxide, potassium, oxide, and chromium oxide and a mixture of iron ferrite and an oxide of a metal selected from the group consisting of cerium zinc, manganese, lead and mixtures thereof. Other oxidative dehydrogenation components include a combination of the oxides of chromium, molybdenum and phosphorus or the oxides of niobium, vanadium and molybdenum. The zeolite and oxidative dehydrogenation component can be present in separate zones, in a single zone, or preferably a composite mixture of the two is prepared by ion exchange or at least partial impregnation of the dehydrogenation component into the zeolite material.
U.S. Pat. No. 4,288,645 to Wagstaff discloses the preparation of aromatic hydrocarbons and hydrogen from a lightweight hydrocarbon feed containing at least 50 weight percent propane. Conversion is effected at a temperature of 400.degree.-700.degree. C. and a pressure of between 5 and 10 bars in the presence of a crystalline silicate containing zinc as a promoter. The zinc is present in an amount within the range of 0.05-20 weight percent, preferably 0.1-5 weight percent, and may be incorporated into the silicate by ion exchange or by impregnation. U.S. Pat. No. 4,291,182 to Dautzenberg et al discloses a process similar to that found in the Wagstaff patent with the exception that the feed stream contains more than 50 weight percent butanes.
U.S. Pat. No. 4,403,044 to Post et al discloses a large number of conversion techniques including aromatization procedures employing feed streams selected from the class of carbon monoxide and hydrogen mixtures, acyclic organic compounds, aliphatic and/or cycloaliphatic hydrocarbons and mixtures thereof. A wide variety of silicalite based catalyst systems are disclosed for use in the conversion techniques of Post et al. The catalyst systems, based on silicalite as the carrier, include metal or metal combinations of nickel, copper, zinc, cadmium, platinum, palladium, nickel-tungsten, cobalt-molybdenum, nickel-molybdenum, zinc-palladium, zinc-copper, and zinc-rhenium. Other metal combinations include iron-chromium oxide, and zinc oxide-chromium oxide. Deposition of the metal combinations on the silicalite may be by impregnation.